DEC_RATE Readback Failure

Hi,

The ADIS1650x has two types of registers - basic data registers, which can always be read back with a read command after the IMU stall time (15us), and configuration registers, which trigger additional processing on the IMU - this includes DEC_RATE, MSC_CTRL, and other similar registers. For these configuration registers, the register value is only updated once the additional processing has completed, and the IMU has returned to normal operation. At this point, you can read the register (DEC_RATE) and check that the correct configuration value was applied.

If you have access to the data ready signal you can detect the IMU returning to normal operation by setting up an interrupt or similar on the data ready active edge, which indicates fresh inertial data is available. You could then read DEC_RATE to verify the value was written correctly, then continue any other configuration of the IMU. If you don't have access to data ready (which I would highly recommend for data synchronization), you can poll DEC_RATE until you read the correct value or reach some timeout threshold.

Regards,

-Alex

For future reference, I've highlighted all control registers in the register map, which will show this behavior.

Note, GLOB_CMD is write-only, so you cannot read back the command bits written.

As an example, I've highlighted the behavior of writes to MSC_CTRL and DEC_RATE in the logic analyzer captures below:

Note, the delay from the register value updating to the new sample being available is driven by the IMU sample rate - in the DEC_RATE write capture, there is an approx. 1ms delay, due to the ODR of 1KHz (2KHz / (1+1)). In the MSC_CTRL capture, the delay is approximately 500µs, based on the default ODR of 2KHz.